Conventionally, espresso coffee beverage is prepared by forcing heated water at around 90 to 96 degrees Celsius through ground coffee, under an atmospheric pressure of between 8 to 9 atmospheres. Pump pressure is applied to heated water in a boiler which is forced through ground coffee typically contained in a coffee basket (or sometimes referred to as a delivery filter). The coffee basket may be built in or mounted on an espresso machine.
It is well recognised that there are three factors governing the quality and consistency of the espresso coffee beverage produced by an espresso machine. They include:
1) grinding—which affects the fineness or coarseness of the ground coffee;
2) pack pressure—which refers to the pressure applied to the ground coffee contained in the coffee basket; and
3) dosage—the amount of ground coffee contained in the coffee basket.
Factors 1) and 2) above can be controlled easily by a barista. Factor 3), however, is difficult to control with any precision or consistency. For example, if the coffee basket of a commercial espresso machine holds a nominal 20 grams of ground coffee, a dose variation of plus or minus 0.5 grams would significantly affect the quality and consistency of the flavour of the extracted espresso beverage.
There are three traditional methods to control the dose of ground coffee. These are:
1) use of a plurality of volumetric chambers provided in a ‘dosing chamber’ which may be found in almost all commercial coffee grinders;
2) use of an adjustable grinder, in which the duration of grinding time may be predetermined and adjusted;
3) manually sweeping a set amount of excess coffee from the unpacked ground coffee already contained in a coffee basket. It is important to note that in this circumstance, it is the ‘unpacked’ ground coffee that is swept.
Method 1) has a disadvantage that, regardless of the level of ground coffee in the dosing chamber, the amount of dispensed coffee is never consistent enough to produce doses of ground coffee with a high degree of precision. This is due to a number of factors, such as the cleanliness of the exit port of the dosing chamber, the rate at which the barista operates the dosing lever on the carousel of the dosing chamber, the moistness of the ground coffee (depending on the degree of hydration of the ground coffee which in turn depends on the duration of time for which the ground coffee is left in the dosing chamber), and the amount of coffee wasted or lost over the sides of the coffee basket during dosing. This method is believed to have a consistency of plus or minus 2.0 grams.
Method 2) has the shortcoming that the amount of coffee ground and ejected along a horizontal port of the grinder body varies greatly from operation to operation as it relies on consistent packing of coffee from the burrs of the grinder to a point where the ground coffee falls over the edge of the port into a dispensing chamber. It should be noted that coffee is a slightly oily substance and as such tends to clump together in a random fashion. This random clumping means that the amount of ground coffee that falls from the port into the chamber would and could never be the same, even though the grinding burrs are operated for exactly the same duration of time. This method is believed to have a consistency of plus or minus 1.5 grams.
The disadvantage and shortcoming of methods 1) and 2) above mean that most users resort to method 3). Method 3) has the drawback that it is a manual operation and depends on the barista collapsing the ground coffee in the basket by tapping or dropping the coffee basket several times on a hard surface to settle the ground coffee to the same volume, and then sweeping off excess coffee at a constant speed each and every time. This is virtually impossible to achieve. This method is believed to have a consistency of plus or minus 1.0 gram.
It is therefore an object of the present invention to provide a tool that may alleviate the disadvantages, shortcomings or drawbacks of the abovementioned prior art or at least provide the public with a useful alternative.